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Ideal Free Distribution Author(S): Mark Moritz, Ian M Mobile Pastoralists in the Logone Floodplain Distribute Themselves in an Ideal Free Distribution Author(s): Mark Moritz, Ian M. Hamilton, Yu-Jen Chen, and Paul Scholte Source: Current Anthropology, Vol. 55, No. 1 (February 2014), pp. 115-122 Published by: The University of Chicago Press on behalf of Wenner-Gren Foundation for Anthropological Research Stable URL: http://www.jstor.org/stable/10.1086/674717 . Accessed: 25/01/2014 08:42 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The University of Chicago Press and Wenner-Gren Foundation for Anthropological Research are collaborating with JSTOR to digitize, preserve and extend access to Current Anthropology. http://www.jstor.org This content downloaded from 68.250.191.217 on Sat, 25 Jan 2014 08:42:43 AM All use subject to JSTOR Terms and Conditions Current Anthropology Volume 55, Number 1, February 2014 115 Mobile Pastoralists in the Logone to the same amount of resources. In assessing the distribution Floodplain Distribute Themselves of grazing pressure over available common-pool resources, we use the ideal free distribution as an indicator of manage- in an Ideal Free Distribution ment of these resources in a situation in which pastoralists Mark Moritz, Ian M. Hamilton, Yu-Jen Chen, and are committed to an ethos of open access to common-pool Paul Scholte grazing resources (Moritz et al. 2013). Pastoralists’ use of common-pool grazing resources in the Department of Anthropology, The Ohio State University, Logone floodplain is best described as open access as there 174 West 18th Avenue, Columbus, Ohio 43210-1106, are no institutions that regulate pastoral use of and access to U.S.A. ([email protected])/Department of Evolution, the floodplain (Moritz et al. 2013). On the contrary, pastor- Ecology, and Organismal Biology, Department of Mathe- alists emphatically argue that access is open for everyone, and matics, The Ohio State University, 390 Aronoff Laboratory, every year, after the water recedes, thousands of Arab and 318 West 12th Avenue, Columbus, Ohio 43210, U.S.A./De- FulBe pastoralists from Cameroon, Nigeria, and Niger move partment of City and Regional Planning, The Ohio State with more than 200,000 cattle into the Logone floodplain University, 275 West Woodruff Avenue, Columbus, Ohio (Seignobos and Iye´bi-Mandjek 2000; Zborowski 1996). 43210, U.S.A./c/o Nieuwe Teertuinen 12C, Amsterdam, LV Open access to common-pool resources has been equated with 1013, the Netherlands. This paper was submitted 7 IX 12, the tragedy of the commons (Hardin 1968). However, critics accepted 22 VII 13, and electronically published 18 XII 13. have argued that Hardin confused commons with open access CAϩ Online-Only Material: Supplement A or unmanaged common-pool resources (Ciriacy-Wantrup and Bishop 1975; McCay and Acheson 1987; Ostrom 1990). More- We examined whether mobile pastoralists in the Logone over, Ostrom (1990) has shown that common-pool resources floodplain of Cameroon distribute themselves according to can be managed sustainably as common property regimes the ideal free distribution (IFD), which predicts that the num- using game-theoretical models and a wide range of empirical ber of individuals in each area is proportional to the quality cases of successful commons. The current consensus in the and quantity of resources in each area and that all individuals literature on pastoral systems is that in most cases common- have access to the same amount of resources. We used the pool resources are managed as common property regimes but concept to assess the distribution of grazing pressure over also that open access will lead to a tragedy of the commons available common-pool resources as evidence of a complex (Galvin 2009; Homewood 2008). adaptive system in which the spatial distribution grazing pres- Here we will present evidence in support of our hypothesis sure is adjusted to the distribution of resources through in- that the management system in the Logone floodplain is a dividual decision making and passive coordination of move- self-organizing complex adaptive system (Moritz et al. 2013). ments among individual pastoralists. We used a combination As evidence for management of common-pool resources we of spatial and ethnographic approaches to study the distri- expect to see that the distribution of grazing pressure is pro- bution of resources and mobile pastoralists in the Logone portional to the distribution of resources within the floodplain floodplain in 5 successive years and found evidence for an as in an ideal free distribution. IFD in 3 years (2008–2009 and 2012) and an approximation of an IFD in years in which pastoralists were terrorized by The Ideal Free Distribution Model armed bandits (2010) and the government reestablished se- curity (2011). The findings support our hypothesis that there The ideal free distribution is a simple and elegant game the- is a self-organizing management system in which pastoralists oretic model that lies at the basis of many other behavioral distribute themselves effectively over the available resources. ecology models that explain the relationship between animal behavior and population dynamics (Fretwell and Lucas 1969; Sutherland 1996). The IFD model predicts how animals In this article we examine pastoral management of common- should distribute themselves over resource habitats or patches. pool grazing resources in a complex social-ecological system. The two main assumptions in the IFD model that give it its Specifically, we examine whether mobile pastoralists in the name are (1) individuals have complete knowledge about the Logone floodplain in the Far North Region of Cameroon resource quality and quantity of each patch (ideal assumption) distribute themselves according to the theory of the ideal free and (2) individuals are free to move to any patch (free as- distribution (IFD; Fretwell and Lucas 1969), which predicts sumption). When those conditions are met, the theory pre- that individuals will settle first in habitats with high-resource dicts that individuals should be distributed such that no in- density and that, at any given time, all individuals have access dividual can gain more resources by moving to a different ᭧ 2014 by The Wenner-Gren Foundation for Anthropological Research. patch. However, empirical studies of fish and birds have not All rights reserved. 0011-3204/2014/5501-0006$10.00. DOI: 10.1086/ always found support for the model (Sutherland 1996). 674717 There are many different versions of the IFD model, but This content downloaded from 68.250.191.217 on Sat, 25 Jan 2014 08:42:43 AM All use subject to JSTOR Terms and Conditions 116 Current Anthropology Volume 55, Number 1, February 2014 the depletion model is the most appropriate IFD model to Ideal free models do not necessarily alleviate the tragedy examine the pastoral use of forage in the Logone floodplain of the commons. Indeed, in depletion models, depletion may (Hamilton 2010b; Sutherland and Anderson 1993). There are become severe over the whole landscape, as even very poor several predictions that arise from this model. First is that habitats become occupied (Sutherland 1996). However, we occupied habitats have higher resource density than do un- argue that (1) because pastoralists live in an open system in occupied habitats at any point in time, because high-resource which they can move within and out of the floodplain, the habitats are occupied first. Second, the variance in standing number of available habitats becomes very large at large spatial resource quality of occupied habitats should be lower than scales and (2) in the spatiotemporal patterns of resource de- the variance in resource quality of unoccupied habitats, be- pletion and renewal, in which depleted habitats are renewed cause foragers will tend to deplete all occupied habitats to the and the spatial distribution of herders on the floodplain is same quality while, in unoccupied habitats, current resource reset by the onset of the rainy season and flooding, full oc- quality is unaffected by depletion. Finally, there should be a cupancy and severe depletion of all habitats in the limited positive correlation between total resources in a habitat (re- time of the dry season is unlikely. In other words, we expect source density # area) and total number of foragers in a that over a wide range of conditions, individuals can do better habitat. Under a model incorporating only depletion, resource by moving rather than by increasing intensity of exploitation quality per unit area should be equal in all occupied habitats; in a given habitat. We thus expect to find an ideal, free-type however, if habitats vary in area, larger habitats should include distribution when mobile users with complete information, more individuals (Flaxman and deRoos 2006; Fretwell and freedom and ability to move, independent and individual Lucas 1969). decision-making capabilities, and a preference for habitual The concept of the IFD has been primarily used in behavioral campsites have open access to depletable common-pool re- ecology studies to examine habitat selection and foraging strat- sources that are highly variable in space and time. Such a egies of animals (Hamilton 2010a; Kennedy and Gray 1993; distribution will be resistant to strategies that overselect or Sutherland 1996), but it is now also used to study the mobility overstay in certain habitats, because the costs of overusing and settlement patterns of human populations (Kennett, An- these habitats fall most heavily on the individuals that overuse derson, and Winterhalder 2006; Winterhalder et al.
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